The present invention generally relates to marked region recognition apparatuses and more particularly to a marked region recognition apparatus which can designate a region of a document image by a mark and carry out different image processings inside and outside the designated region. The marked region recognition apparatus is especially suited for use in an image processing part of a digital copying machine.
In a digital copying machine, a document image data which is read from a document is subjected to an image processing in the form of an electrical signal. For this reason, the digital copying machine is capable of making image processing and image editing which cannot be made on an analog copying machine. Conventionally, there is a digital copying machine which carries out different image processings inside and outside an arbitrary closed region of a document image which is marked by a marker pen or the like. In such a digital copying machine, it is possible to carry out image processings such as erasing the inside of the marked region and turning over the black and white inside of the marked region. In order to carry out such image processings, it is necessary to recognize the inside and the outside of the marked region which is the arbitrary closed region surrounded by the mark.
For example, a Japanese Laid-Open Patent Application No. 61-109374 proposes a marked region recognition apparatus. According to this proposed marked region recognition apparatus, there is provided a mark detection means for detecting a mark from a document image data which is read by a reading means and is continuous in a main scanning direction. The marked region is recognized by switching a marked region recognition result as the inside and the outside of the marked region every time a mark signal ends. In addition, the marked region recognition results for one line are stored, and no mark region is recognized unless the mark signal is obtained when a previous line is not a marked region.
However, the proposed marked region recognition apparatus suffers from the following disadvantages. That is, when a rectangular region is marked by a mark 2 as shown in FIG. 1A, it is possible to normally process this region and recognize the inside of a marked region 1 as indicated by a hatching in FIG. 1B. However, when a non-rectangular region is marked by the mark 2 as shown in FIG. 2A, the inside of the marked region 1 is erroneously recognized as indicated by a hatching in FIG. 2B.
On the other hand, when the mark 2 does not mark a closed region as shown in FIG. 3A, the marked region 1 is erroneously recognized as indicated by a hatching in FIG. 3B. In FIGS. 1B, 2B and 3B, MS denotes a main scanning direction and SS denotes a sub scanning direction.
Therefore, in order to prevent an erroneous recognition of the marked region, it is necessary to restrict the shape of the mark and also limit the user who makes the marking to a person familiar with the rules of the marking.